Summary

Mitogen-activated protein kinase (MAPK) cascades have essen­tial roles in diverse intracellular signaling processes in plants, animals and yeasts. In plants, MAPK and MAPK-like kinase activities are transiently ac­tivated in response to environmental stresses and plant hormones. In addi­tion, transcription of genes encoding protein kinases involved in MAPK cascades is upregulated by environmental stresses. A possible MAPK cas­cade of Arabidopsis was identified based on both the yeast two-hybrid anal­ysis and functional complementation analysis of yeast mutants. This MAPK cascade may have important roles in stress signal transduction pathways in Arabidopsis.